Commandlines.txt

Create file
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touch <file>.<ext>
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Quickly view content of file
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# read all to terminal
cat <OPTION> <FILE>

# read all then display page by page -> slow for large file
more <OPTION> <FILE>

# read on-the-fly -> fast even for large file
less <OPTION> <FILE>
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Create directory
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mkdir -p <path>/<target dir>
-p: self-create parent dir if not existed
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Remove directory
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rm -rf <target dir>
-r: recursive
-f: forced
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Move to directory
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cd <target dir>

# Move to home
cd
or
cd ~

# Move out
cd ..

# Move back to previous dir
cd -
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Copy all
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# Copy all but change owner to current one (forced + recursive)
cp -fr [source] [dest]
or
# Copy all & keep everything as-is (ex: owner, permission...)
cp -a
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Edit text file
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sudo vi <file> //if user doesn't have file editing permissions

# For inserting
Press i //Do required editing

# For exiting
Press Esc
    :wq //for exiting and saving
    :q! //for exiting without saving
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All about access permission
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# View access permission:
ls -l --> view long list of contents

# Format:
-rwx---rwx -> divided into 4 parts:
_ -: file(-) or dir(d) or link(l)
_ rwx: owner permissions - read(r) or write(w) or executable(x) or non(-)
_ ---: group
_ rwx: other users

# Change access permission:
_ for owner: chmod <add(+) or remove(-)><w/r/x> <file/dir>
_ for group: chmod g+wrx <file/dir>
_ for others: chmod o+r <file/dir>
_ for all:  chmod ugo/a+rx <file/dir>

# Extra: replace <+/-><w/r/x> by below numeric code
    0 = ---
    1 = --x
    2 = -w-
    3 = -wx
    4 = r--
    5 = r-x
    6 = rw-
    7 = rwx
-> ex: chmod 777 <file/dir> => give wrx permission for all users

# Change owner/group of file/dir:
_ change group: chgrp <group> <file/dir>
_ change owner: chown <user> <file/dir>
_ change both: chown <user>:<group> <file/dir>

# References:
https://help.ubuntu.com/community/FilePermissions
https://www.pluralsight.com/blog/it-ops/linux-file-permissions
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Make file executable
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chmod +x <file>
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Switch between virtual console (tty)
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sudo chvt x (x = 1 to 6)

# to check tty# & which user is logging in it
who
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Kill X server = Stop lightdm/gdm/kdm 
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# To stop:
sudo service gdm stop (or use lightdm or kdm instead)
or
sudo systemctl stop gdm

# To start/restart:
sudo service gdm start/restart
or
sudo systemctl start/restart gdm
or
startx
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To solve error with Nouveau
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sudo update-initramfs -u
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Install dkms and build-essential
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sudo apt-get install build-essential dkms
# Unnecessary for newly installed OS
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Check for opengl version
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sudo apt install mesa-utils
glxinfo | 
"OpenGL version"
glxinfo | grep '^direct rendering:'
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Check for installed dkms kernel module
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dkms status
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All about gcc
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Install:
sudo apt-get install gcc-8 g++-8

Having gcc redirected automatically to gcc-8:
sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-8 800 --slave /usr/bin/g++ g++ /usr/bin/g++-8

Set default:
sudo update-alternatives --config gcc
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Ctrl+C: To stop current jobs (put it to background process)
top: View running processes
htop: Better tool to view running processes
ps -A: list of running processes
jobs: view suspended jobs


Check for gcc version which is used to compile linux kernel
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cat /proc/version
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Add PPA launchpad driver
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sudo add-apt-repository ppa:graphics-drivers/ppa

Remove:
sudo add-apt-repository --remove ppa:graphics-drivers/ppa
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Check for openCV version
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pkg-config --modversion opencv
or
/usr/bin/opencv_version
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Check for ROS version
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rosversion -d
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Check for cuda version
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cat /usr/local/cuda/version.txt
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Check for nvidia driver version
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cat /proc/driver/nvidia/version
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Check for cuda compiler version
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nvcc --version
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Check for Python version
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List installed python:
ls /usr/bin/python*

View version:
For python2: 
$ /usr/bin/python -V
OR
/usr/bin/python --version

For python3: 
$ /usr/bin/python3 -V
OR
/usr/bin/python3 --version
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Check for connected camera
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ls -ltrh /dev/video*
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Check for USB dev
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lsusb
or
ls -l /dev | grep ttyUSB ->> used to detect Arduino
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Add user to group
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sudo usermod -a -G [group] [user]
then logout & login again for the permission to take effect
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Check for connected devices with open port 22
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sudo nmap -sS -p 22 192.168.0.0/24
_ /24: first 24 bits are masked (192.168.0) = subnet 255.255.255.0
_ /16: first 16 bits are masked (192.168) = subnet 255.255.0.0
_ the rest (unmasked) bits is host
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Check for open port of target devices 
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sudo nmap -sS 192.168.x.x
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Sync time between different machines
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Check time different:
ntpdate -q [client ip]

Restart chrony:
service chrony restart

Tracking:
chronyc tracking

View sources list:
chronyc sources -v

Check client list:
sudo chronyc clients

Other:
systemctl enable chronyd.service
systemctl start chronyd.service
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View system time
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timedatectl
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Fix arduino shortcut
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sudo chown YourUserName /path/to/icon/arduino-arduinoide.desktop
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Seach for files/dir
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find <in where>
-type [bcdpfls]: type of target 
    f: a regular file
    d: directory
    l: symbolic link
    c: character devices
    b: block devices
    p: named pipe (FIFO)
    s: socket
-name <name>: name include <name>
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List disks/sectors info
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sudo lsblk -o NAME,FSTYPE,SIZE,MOUNTPOINT,LABEL
sudo fdisk -l </dev/sda>
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Mount partitions
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sudo mount /dev/sdb1 /media/SSD

additinal options:
-o rw,norecovery
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View cmd attached to alias
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type [alias]
or
alias ->> display all active alias
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Scan for serial connection
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dmesg | egrep --color 'serial|ttyS'
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Bring up wireless devices
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sudo ifconfig wlan0 up
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Add network drive/directory
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sftp://nvidia@192.168.0.107/media/nvidia/SSD
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Install .deb pkg in terminal
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sudo dpkg --install <pkg.deb>
or
sudo dpkg -i <pkg.deb>
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Backup disk
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sudo dd if=/dev/sdb of=~/SDCardBackup.img
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Change to root user
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sudo -i
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Check file system consistency
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dosfsck /dev/sdb
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View mainboard info
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sudo dmidecode -t baseboard
or
sudo dmidecode -t 2
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Search for apt package
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apt-cache search <pkg name>*
or
apt-cache policy <pkg name>*
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Get author description about cmd in terminal
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man <cmd>
Ex: man sudo
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Get estimate file space usage
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du <option> <files>
Ex: du -hd1
-d, –max-depth=N : print total for directory only if it is N or fewer levels below command line argument
-h, –human-readable : print sizes in human readable format
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pipe output from "this" to input of "that"
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Use "|"
Ex: du -hd1 | sort -rh | head -10
~ du_stdout =>> sort->sort_stdout =>> head->head_stdout
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Modify screen resolution
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Show list of monitors and their connectivity:
xrandr --listmonitors
or
xrandr    -> show all connectivities & their available settings

Scale output res by 1.2
xrandr --output eDP-1-1 --transform 1.2,0,0,0,1.2,0,0,0,1
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Get data from/to server
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curl <options> <link to server contents>
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Create symlink
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ln -s <target/source path> <dest path>
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View max pipe buffer size
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cat  /proc/sys/fs/pipe-max-size
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Determine current version of kernel
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uname -a
uname -r
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Install the headers for the running kernel
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sudo apt-get install linux-headers-$(uname -r)
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View graphic interfaces or check for its error
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lspci -k | grep VGA
sudo lshw -c video
sudo lshw -C display

lspci |grep -i nvidia
dmesg | grep NVRM
lspci -v -s $(lspci | grep ' VGA ' | cut -d" " -f 1)
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Get online dir/files
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wget -r -np -R "index.html*" -P <link to saved dir> <link to taget dir/file>

params:
-P <link to saved dir> or --directory-prefix=<link to saved dir>: save content to target dir
-np or --no-parent: Not recursively download content in parent dir
-R or --reject "index.html*": Reject any file like <that>
-r or --recursive: recursive retreiving
-nH or --no-host-directories: Disable generation of host-prefixed directories
--cut-dirs=<number>: Ignore number directory components (top down)
-l <depth> or --level=depth: Specify recursion maximum depth level depth
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Compress files/folder
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# using zip
zip <output name> <files>
zip -r <output name> <folder>

# Using tar
tar -czvf <output name>.tar.gz <files/folder 1> <files/folder 2>
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Extract compressed file
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# Extract single file:
tar -xvzf <file>
unzip <file>

# Extract multiple file:
cat *.tar.gz | tar zxvf - -i
unzip \*

# Extract to target dir
unzip <file> -d <target dir>
tar -xvJf <file> -C <target dir>
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Filter out output list
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add { | grep <target name>} after command
or
grep -e <target1> -e <target2> -e <target3> for multiple targets
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Create initial ramdisk images for preloading modules (initrd)
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dracut
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Generate ramdisk (initframfs)
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dracut /boot/initramfs-$(uname -r).img $(uname -r)
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Rebuild grub
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sudo grub-mkconfig -o <Output file>[/boot/efi/EFI/centos/grub.cfg]
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Control all services
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use systemctl or service 

View stats/stop/start/restart/enable/dissable:
sudo systemctl <options> <svc>
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View users info
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w
who
users
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View listening port
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ss -tulp
netstat -tulpn
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Fix/Check broken dd image
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fsck -y /<absolute path to img file>
or
fsck.ext4/exfat/msdos...
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View deb source repo
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nano /etc/apt/sources.list
or
ls /etc/apt/sources.list.d/
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View info (ssid, MAC...) of wireless device
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iw <dev name (ex: wlan0)> info
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Log out all current user sessions
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loginctl terminate-user <User Name>
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Check for wayland or x11 session is being used
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loginctl show-session $(loginctl | grep $(whoami) | awk '{print $1}') -p Type
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Record output to log file
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<cmd> 2>&1 | tee <log_file>.log
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View pkgs installing history
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# View all
grep " install " /var/log/dpkg.log

# View recent installs
awk '$3~/^install$/ {print $4;}' /var/log/dpkg.log

$ View install cmd only (exclude dependencies)
grep " install " /var/log/apt/history.log
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xargs usages - Repeat cmd with multiple inputs
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# Move multiple files to other place (in case mv not works: Argument list too long)
ls | xargs mv -t <dest>

# Repeat cmd (ex: <app> <argv 1> <argv 2>
ls | xargs -l <app> <argv 1>
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List all pci devices
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lspci -vv
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Add & remove user
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sudo adduser <username>
sudo deluser --remove-home <username>
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View hw specs
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sudo lshw -short
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Fully reset git repo
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git reset --hard && git clean -ffdx
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